[IMP]: point_of_sale: price control can be enabled without installing pos_hr in pos_config

Before: to enable price control, we first have to install the `pos_hr` module by
enabling the "Authorized Employees" option. Only then was the price control option
visible. It was then possible to enable/keep the price control option while having
the "Authorized Employees" disabled. This behavior did not make sense.

After: Price control is now visible and independent from the `pos_hr` module.
The feature was already implemented in the `point_of_sale` module but the option (in the `pos_config` view) was put in the `pos_hr` module.

Task ID: 2419637